The present invention provides a process for the preparation of thiazole derivative. More particularly, the present invention relates to a process for the preparation of 4-methyl-5-formyl-thiazole of the formula (I). 
4-Methyl-5-formyl-thiazole of the formula (I) is a useful key intermediate in the preparation of Cefditoren pivoxil of the formula (II), which is a well known antibiotic. 
Harrington et al (J. Chem. Soc., (1939) 443-446) described a process for the preparation of 4-methyl-5-formyl-thiazole of the formula (I), starting from ethyl 4-methylthiazole-5-carboxylate which was converted through the amide to the nitrile, which in turn was converted to the aldehyde. The process involves the preparation of the nitrile compound by using POCl3, which is highly corrosive, hazardous and difficult to handle in large scales.
Yokoyama et al (Stud. Surf. Sci. Catal., (1994), 90, 47-58) reports a process for the direct hydrogenation of aromatic carboxylic acid to the corresponding aldehydes. The catalyst used is modified zirconia.
EP patent number 0 343 640 claims a process for the preparation of heterocyclic aldehyde from the corresponding carboxylic acid and its derivatives using a catalyst consisting of an oxide of Zinc, Yitrium, lanthanides or Group 4A elements. The oxides of these metals are prepared at very high temperature such as 200 to 900xc2x0 C. Methyl 4-methylthiazole-5-carboxylate was hydrogenated using an oxide catalyst composed of chromium, zirconium to produce 4-methylthiazole-5-carboxaldehyde also at very high temperature ranging from 200 to 700xc2x0 C., which makes the process industrially non-workable.
JP 45036908 discloses a process for the preparation of 4-methyl-5-hydroxymethyl thiazoles from 4-methyl-5-(ethoxycarbonyl) thiazoles using LiAlH4 and diethylether. The process suffers the following disadvantages: The reducing agent, LiAlH4 cannot be handled in the large operations as it is an hazardous reagent. This problem has been overcome by the use of sodium borohydride, in the presence of AlCl3 in the present invention as the rate of evolution of hydrogen in the process is controllable and hence, the reaction as a whole is easy to handle.
To overcome the problems associated in the preparation of 4-methyl-5-formyl-thiazole of the formula (I), we focussed our research to develop a process, which uses non-hazardous materials, industrially workable at ambient temperature and safe to use.
The main objective of the present invention is to provide a process for the preparation of 4-methyl-5-formyl-thiazole of the formula (I), which is useful as an intermediate in the preparation of Cefditoren.
Another objective of the present invention is to provide a process for the preparation of 4-methyl-5-formyl-thiazole of the formula (I), which is commercially viable, high yielding, and with high purity of the product.
The present invention relates to a process for the preparation of 4-methyl-5-formyl-thiazole of the formula (I) 
which comprises oxidising the 4-methyl-5-hydroxymethyl thiazole of the formula (IV) to 4-methyl-5-formyl-thiazole of the formula (I), using an oxidizing agent at a temperature in the range of xe2x88x9210xc2x0 C. to 50xc2x0 C., in the presence of a solvent.
In another embodiment of the present invention, there is a provided a process for the preparation of 4-methyl-5-hydroxymethyl thiazole of the formula (IV), which comprises reducing the thiazole ester of the formula (III), wherein R represents (C1-C4) alkyl group such as methyl, ethyl, n-propyl, iso-propyl, tert-butyl to 4-methyl-5-hydroxymethyl thiazole of the formula (IV), using sodium borohydride in the presence of AlCl3 and a solvent, at a temperature in the range of xe2x88x9220xc2x0 C. to 90xc2x0 C.
The reaction scheme described above is as shown below. 